In general, a signal transmission apparatus uses channel information between the signal transmission apparatus and a signal reception apparatus in a wireless communication system, thereby significantly improving total system performance of the wireless communication system.
Differing with a time division duplexing (TDD) communication system for acquiring channel information on a downlink channel by using channel information on an uplink channel, the signal transmission apparatus should receive feedback information indicating channel information from the signal reception apparatus since the uplink channel and the downlink channel are independent from each other in a frequency division duplexing (FDD) communication system in which a frequency used in the uplink and a frequency used in the downlink are different from each other. Here, resources used for transmitting the feedback information deteriorate resource efficiency of the FDD communication system and cannot help being limited, and thus an efficient feedback scheme is required. The feedback information is generated by quantizing the channel information, and resources used for transmitting/receiving the feedback information are feedback resources.
When the signal transmission apparatus uses the feedback information, the performance of the FDD communication system deteriorates. Particularly, when the FDD communication system corresponds to a multi-user multi-antenna system for simultaneously providing a service to a plurality of UEs, the performance more seriously deteriorates due to the use of the feedback information. Accordingly, the need for the efficient channel feedback scheme further increases in the multi-user multi-antenna system.
Meanwhile, the performance of the wireless communication system using limited feedback resources may increase through selection of an efficient UE. Here, each of the UEs that receive the service from the wireless communication system should transmit not only feedback information but also performance information related to the performance, which each of the UEs can acquire, to a base station (BS) in order to enable the BS to efficiently select the UE. Further, the BS may select an optimal UE based on the feedback information and the performance information received from each of the UEs and provide the service to the selected UE.
Meanwhile, research on a large MIMO (Large-MIMO) using many antennas to increase the performance of a multi-antenna system is being actively progressed. However, in the Large-MIMO communication system, since a channel dimension increases, an amount of feedback information which should be received from UEs significantly increases. Further, when the number of UEs increases, a UE selection and transmission beam design scheme having low complexity and acquiring high performance is required.
Meanwhile, in the conventional wireless communication system, research of quantitatively analyzing system performance deterioration of the wireless communication system when the number of feedback information bits, which can be used per UE, is given has been mainly progressed. Further, in the conventional wireless communication system, research on how to quantize required feedback information under given feedback capacities and research on how to form a transmission beam based on the quantized feedback information have been mainly progressed.
Moreover, in the conventional wireless communication system, the use of multiple antennas was considered in the research on the feedback information, but the Large-MIMO scheme using a relatively large number of antennas, for example, dozens or more of antennas has not been considered.
In addition, in the conventional wireless communication system, research on which UE should be selected and how to apply a beamforming scheme when many UEs exist under a limited feedback environment has not been actively progressed.
Accordingly, the need for a scheme for performing a UE selection operation and a beamforming operation suitable for a wireless communication system using a beamforming scheme while using a MIMO scheme has arisen. Further, the need for a scheme for transmitting/receiving feedback information to efficiently perform a UE selection operation and a beamforming operation in a wireless communication system using a beamforming scheme while using a MIMO scheme has arisen.
Meanwhile, the aforementioned information is disclosed only as background information for helping in understanding the present disclosure. No decision and no opinion on whether any of the above content can be applied as the prior art of the present disclosure have been made yet.